Over the years, I've looked at enough of the Nebraska test reports to notice a couple things. Testing on concrete will give you some relative idea of fuel use, but as Dutch says, it doesn't compare the efficiency of tracks vs tires very well.

There are enough types of tests run that you can pretty much see how different tractors compare under light load, medium load, heavy load, reduced rpm, drawbar conditions, pto conditions, etc. What all these tests have in common is they are done at a constant rpm.

What I've noticed is the tests don't seem to be designed to test wildly fluctuating loads. The governor on some tractors is designed to kick in faster than on others, which could easily result in different fuel use results under varying loads. I don't have personal experience as to how one brand compares to another in this type of environment, but it's something to consider when getting conflicting information.

Finally, a partisan statement in response to Bern. Deere is advertising significant fuel use improvements on the 8030 series tractors compared to the older series. This is despite the lower emission standards.